Free to download watermarked videos

No, of course not.   You can't publish ANYTHING on YouTube that you don't own.  That would be stealing an artists intellectual property and you could be sued in court for copyright infringement.  A case you would lose by the way. 

I posted this recently in the Premiere Pro forum, and it was moved to the Video Lounge:

https://community.adobe.com/t5/video-lounge-discussions/a-giant-list-of-free-stock-assets-for-video-all-over-the-internet-enjoy/m-p/12712625#M9537

Hopefully it helps...

No, there's a reason why they are watermarked: They are only meant for evaluation.

If you want to use them, you'll have to purchase them - regardless of if you're creating a monetized or non-monetized video.